chore!(firewall): iptables logger level is set at FIREWALL_IPTABLES_LOG_LEVEL

- firewall log level is still fully controlled by `LOG_LEVEL`
- iptables log level defaults to `info` even if global log level is `debug` to minimize the amount of debug logs
- iptables log level is only set to debug if retro-compatible `FIREWALL_DEBUG=on` or if `FIREWALL_IPTABLES_LOG_LEVEL=debug`

internal/configuration/settings/settings.go

@@ -120,10 +120,10 @@ func (s *Settings) OverrideWith(other Settings,
 func (s *Settings) SetDefaults() {
 	s.ControlServer.setDefaults()
 	s.DNS.setDefaults()
-	s.Firewall.setDefaults()
+	s.Log.setDefaults()
+	s.Firewall.setDefaults(s.Log.Level)
 	s.Health.SetDefaults()
 	s.HTTPProxy.setDefaults()
-	s.Log.setDefaults()
 	s.PublicIP.setDefaults()
 	s.Shadowsocks.setDefaults()
 	s.Storage.setDefaults()